Tamerlan Tsarnaev seemed the tamest guy in the gym at Wai Kru Mixed Martial Arts in Boston where he trained to be an Olympic boxer: He didn’t drink or smoke; he thought kicking in mixed martial arts was “dirty;” his muscular body didn’t bear garish tattoos like his opponents; and he rarely took his shirt off for fear women would get the wrong idea.

“I’m very religious,” he said in an interview to accompany a 2010 photo essay on his boxing career by Johannes Hirn.

He stopped drinking because of prohibitions of his Muslim faith: “God said no alcohol,” he said at the time. “There are no values any more. People can’t control themselves.”

Praise for self-control and devotion now stand as the public sentiments of the man the FBI says sauntered into a crowd of civilians near the finish line of the Boston Marathon with his younger brother and dropped two homemade bombs designed to kill and maim.

This week started with the 26-year-old Tamerlan Tsarnaev — then unidentified — setting off the bombs that killed three, including an eight-year-old boy, and injuring 183, authorities say. It ended with him dying in a hail of bullets during an immense manhunt during which a campus police officer was killed.

Tamerlan Tsarnaev was dead just as the public was learning he was the name and the face behind “Suspect 1,” seen at the marathon wearing a black ball cap.

A video image of him dead, face down on a dark street in a Boston suburb, that greeted those waking Friday to the dramatic overnight news, was soon contrasted with the pictures of him as a dedicated boxer preparing for the National Golden Gloves boxing tournament.

He hoped to make the U.S. Olympic boxing team, since his native Chechnya was not recognized as an independent state, he told Mr. Hirn. He preferred to join the U.S. team rather than compete for Russia, he said. But his choosing America over Russia did not mean he was comfortable in his adopted home.

“I don’t have a single American friend; I don’t understand them,” Tamerlan Tsarnaev said, although he had acclimatized enough to show off his Mercedes and say he enjoyed the movie Borat, an outlandish comedy poking fun at both America and Kazakhstan, two countries he has lived in.

The nexus of Chechnya, the United States and Russia are now being probed by investigators who say Tamerlan Tsarnaev travelled to Russia last year and returned to the U.S. six months later.

The visit of the young men to Russia was confirmed by their aunt, Maret Tsarnaeva, who lives in Toronto. Tsarnaeva said Tamerlan Tsarnaev was married to a woman she called a “good Christian,” and had a young daughter, about three years old. Tamerlan Tsarnaev looked after his daughter while his wife worked, she said.

It is not known if his wife is the same woman shown in the photo essay, whom Tamerlan Tsarnaev described as his half-Portuguese, half-Italian girlfriend who converted to Islam: “She’s beautiful, man,” he enthused.

Nor is it known if it is the same woman whom he was charged with hitting in a domestic assault in 2009.

The Tsarnaev family fled Chechnya, in southeastern Europe, in 1994 because of conflict with Russia, and lived in Kazakhstan, where Tamerlan Tsarnaev was apparently born, before arriving in the United States as refugees in 2002, Tsarnaeva said.

The brothers have two sisters who live in the U.S. Their mother, Zubeidat Tsarnaeva, and two uncles remain near Boston, while their father, Anzor Tsarnaev, 46, returned to Russia. Many family members spoke of unspecified problems within the family and alienation from Mr. Tsarnaev.

As children, Tamerlan Tsarnaev and his brother, Dzhokhar, 19, the man called “Suspect 2” in the bomb attacks who was taken into custody Friday night, rode bikes and skateboards on quiet Norfolk Street in Cambridge, Mass.

Tamerlan Tsarnaev worked in a variety store and delivered pizza while he boxed and attended school, including Bunker Hill Community College. He said he wanted to become an engineer. Gene McCarthy, who trained Tamerlan Tsarnaev at the Somerville Boxing Club, described him as a “nice kid” who was “very intelligent” and a good fighter who learned from his father before he came to the gym. “He never lost a bout for me,” said McCarthy, adding that Tsarnaev also played classical piano.

Tamerlan Tsarnaev’s mother said her eldest son “got involved” in religion about five years ago. “He never, never told me he was on the side of jihad,” she told CNN.

The FBI confirmed Friday that agents interviewed Tamerlan in 2011 at the request of a foreign government over suspected ties to an extremist group.

An official says the FBI shared its information with the foreign government, but did not say what country made the request about Tamerlan or why.

Tamerlan Tsarnaev appears to have run a YouTube channel showing interest in radical Islam. He promoted videos of Feiz Mohammad, an Australian former boxer turned radical Muslim preacher who asks that children be raised as jihadists, saying: “Put in their soft, tender hearts the zeal of jihad and a love of martyrdom.”

Tamerlan Tsarnaev also created a playlist called “Timur Mucuraev,” which contains a video by a Russian singer promoting jihad; another entitled “terrorists” and a third called “islam,” according to SITE Intelligence Group.